Chart a course for consolidation

Consolidating storage is a complex, challenging process. Whether you're tackling DAS, NAS or SAN, there are key issues that must be addressed to have a successful storage consolidation project.

Consolidation will be on most it project lists this year and for good reason. The benefits of consolidation are easy to delineate, and the savings can be substantial. Depending on the scope of the project, storage consolidation helps the bottom line by reducing assets, lowering hardware and software maintenance, upping storage capacity utilization, and enabling more effective and efficient storage management.

Unfortunately, storage consolidation isn't as simple as buying a large, enterprise-class storage array and migrating applications to the new platform. In a nutshell, a consolidation project follows the three Ps: process, procedure and policy. Whether a consolidation project involves DAS, SAN or NAS, there's a commonality to the approaches in addition to the expected differences.

Common issues
There are multiple options, protocols and architectures that may be employed to achieve a consolidated storage infrastructure, but we'll use a Fibre Channel (FC) SAN as the option of choice. While not all-inclusive, some of the top items to consider before embarking on a consolidation project include the following:

Tiered storage. It's best to implement a tiered storage infrastructure while consolidating. Much work is required to implement a tiered storage architecture, such as classifying data and understanding the value of data over time. But having the infrastructure in place early on--even if some educated guesses are required for initial application data placement--will reap significant benefits down the road.

Common data protection. It's much more straightforward to create and manage a common data protection scheme for operational and disaster recovery (DR) purposes and for a consolidated storage environment vs. a distributed one. Consider moving large backup jobs to the storage network rather than running them on the LAN. It may also be the perfect opportunity to integrate a disk-based backup architecture. For DR, consider creating a storage tier that seamlessly supports replication to a remote site. In any case, having centralized control and management will simplify and streamline the processes.

High availability. Availability becomes a greater concern because storage consolidation is akin to putting "more eggs in one basket." The storage network should keep running in the event of a minor malfunction such as a host bus adapter (HBA) or cable failure. Techniques such as dual HBAs with multipathing software, dual fabrics and resilient connectivity paths should be implemented if they weren't previously used in the decentralized environment. For areas outside the storage infrastructure, consider server clustering.

Interoperability. Whether consolidating with new equipment or incorporating existing assets, interoperability issues always arise. For example, your FC fabric may be based on the latest and greatest technology, but those two-year-old HBAs in your application servers are no longer supported or need a major microcode/firmware upgrade. Operating system support, especially for older servers handcuffed by legacy application requirements, can also be an issue. Getting an upfront and detailed inventory of the current environment will save a lot of time, as well as avoid aggravation during and after migration to the consolidated infrastructure.

Multiprotocol. You should plan for multiprotocol storage connectivity now. For a consolidated storage infrastructure, this is one of those rare opportunities where you're working with a relatively clean slate, so take full advantage of it. If FICON or iSCSI may be a requirement in the future, ensure that your product selection can accommodate and support multiple protocols. It's even more important to understand the application requirements and performance characteristics of each of the protocols used. For example, FC is supported at multiple speeds today (1Gb, 2Gb and 4Gb), but future speeds (10Gb) may require different products/connectivity options.

Director switches. Think about scalability and cost-effective port density for the new, consolidated storage network. Historically, the fewer the ports on a single FC switch, the more inter-switch links (ISLs) are required to scale the fabric. Newer, director-level switches have impressive port counts--many in the hundreds on a single device. While still maintaining dual fabrics in alignment with the high-availability objectives in a consolidated SAN (many director-level switches also support separate logically segregated fabrics), port density should be a serious consideration to avoid wasting ISLs on interconnectivity.

That doesn't mean a core/edge architecture can't be used to ensure the most cost-efficient use of each port, but the total number of ports dedicated to connectivity, rather than fabric expansion, will make the fabric more cost-effective in the long run. The icing on the cake is that more of these director-level switches allow scaling when needed by adding ports via new blades without interrupting fabric services.

Top three storage consolidation lessons
1. Storage consolidation usually pushes organizational change, such as the formation of a storage management group. Accountability and focus is required to take on this large task, including ongoing management once the consolidation is completed.
2. While the business case seems obvious, matching hard-dollar savings to storage consolidation can be difficult. This is especially true when consolidating DAS to a new million-dollar storage network infrastructure.
3. Understand your current storage environment before proceeding, and understand it in detail. Heading off interoperability issues may become a daily activity during the consolidation project.
Operational issues. If your organization doesn't have a team dedicated to storage management, storage consolidation will surely bring that issue to the forefront. The planning, architecture, design, purchasing, implementation and ongoing support tasks related to storage consolidation are numerous and require specialized skill sets. It's best to formalize an enterprise storage management team, with clear lines of demarcation among IT teams, prior to a consolidation project (see Top three storage consolidation lessons, this page).

While not specific to consolidation, it's important to note that the implementation of an enterprise storage management team will have a cultural effect on your staff. For example, your server team will no longer own the storage attached to their servers (e.g., DAS), and must learn to deal with the new kid on the block--the enterprise storage management team. Similarly, the network team may take issue with not managing all networks, including the storage network. These are significant issues that need to be addressed up front.

Policy planning. Prior to beginning a consolidation effort, policy issues must be addressed. Hand in hand with the justification for the enterprise storage management team is the requirement for strategic and tactical storage policies, along with associated standard operating procedures. One of the more obvious areas is specific to storage provisioning. Assuming the consolidated storage infrastructure is implemented, the next steps are allocating and provisioning storage to the servers and applications that require it. Naming conventions, allocation processes, data protection and documentation are just a few of the tasks related to storage provisioning. "Winging it" at this critical juncture of the consolidation project isn't acceptable. Having policies and procedures in place will make the multiple decisions required in a complex task such as storage provisioning much more straightforward.

Data migration. One consolidation task is to have the consolidated storage infrastructure built and ready to go. A totally different task is to get your application data migrated. Beyond just considering the pure volume of data to be migrated, take a look at some other important items that need to be considered and weighed, such as the number of files (e.g., many small files could make the migration take much longer, depending upon the approach), the different migration options (tape, network, mirror) and the data migration windows. The initial location of the servers and storage is also a major consideration, and often dramatically pares down the available migration options. Conducting dry runs to benchmark how long a data migration may take is strongly recommended; all too often, the data transfer spreadsheets you create are more theoretical than practical.

Risk mitigation. Even the most detailed and well-thought-out storage consolidation projects are full of hidden perils. What if a data migration hiccups in the last minutes of a five-hour data transfer? What if the application testing team finds some post-migration issue that isn't remotely related to the new storage infrastructure? What if the I/O performance in the consolidated environment is taking a beating due to multiple, disparate standalone applications simultaneously hitting the shared, consolidated storage infrastructure? It's important to have Plan B and Plan C ready so you can respond to those "keep our fingers crossed it never happens" scenarios.

Change control. Don't underestimate the level of participation required for storage consolidation. While it may be obvious that internal change-control processes and policies must be strictly adhered to, the number of coordination touch-points for storage consolidation activities is usually higher than for other change activities. For example, a consolidation effort may include the application owner; database, server and network administrators; the enterprise management storage team; and probably the data center manager and a project/program manager or two. Depending upon the activity, storage vendor product engineers may also be part of the equation. Proactive coordination is critical to success.

Unique issues with DAS, SAN and NAS
There are also specific issues that are dependent upon the current state of the storage being consolidated. For example, DAS doesn't require external HBAs, as the storage is internal to the server. If your consolidation project includes many DAS servers and applications, then it's important to determine if those servers have I/O backplane slots for the appropriate number of HBAs. In addition, it's best to standardize on a small number of HBA products--possibly by operating system and/or server type. In a multipathed, high-availability, dual-HBA environment, the cost of these HBAs can have a big impact on the consolidation project budget if a significant number of HBAs are required.

Compared to consolidating DAS, SAN environments offer different challenges. There's a high probability that the consolidated environment won't be new, as the goal is often to utilize as much existing SAN hardware and software as possible. Tough decisions need to be made, such as whether the fabrics should be merged or if it's better to create a totally new fabric.

It may also be necessary to decide if HBAs should be standardized or if old ones should be "grandfathered in" for the sake of capital cost (give operational and management costs due consideration when tackling this issue). And if your SAN comprises a multitude of arrays from different vendors, it's a perfect time to start planning for a tiered storage environment.

Consolidating NAS can range from buying larger filers to moving toward NAS gateways that can use the consolidated SAN infrastructure for its storage requirements. It may also be a good time to take a serious look at iSCSI, depending on the block- or file-based requirements of your specific applications. Give careful consideration to the storage services you're using on the new consolidated storage infrastructure and see if you can leverage some of the same software in your NAS environment, rather than having separate sets of software for each environment.

Other issues to consider include the opportunity to revisit storage virtualization strategies, the pros and cons of doing server and storage consolidation at the same time, and understanding what applications/environments may not benefit from consolidation.

The cost savings of storage consolidation can result in a fairly rapid return on investment. But a lot of upfront work is required to ensure a successful deployment that reaps the benefits of these activities.

This was first published in April 2005
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